The present invention relates to a triticale seed, a triticale plant, a triticale cultivar and a triticale hybrid. This invention further relates to a method for producing triticale seed and plants. All publications cited in this application are herein incorporated by reference.
Triticale (Triticale hexaploide L.) is a crop species resulting from a cross between wheat (Triticum) and rye (Secale). It is a man-made crop in that plant breeders must physically make crosses and then manipulate the resultant offspring to obtain a self-fertile plant. Triticales are agronomically desirable due to their ideal combinations of the yield and quality advantages of common wheat, and the hardiness, pest tolerance, and adaptability of rye.
Hybrids of wheat and rye date back to the late 1800's, however early attempts to cross wheat and rye produced only sterile offspring, so for many years triticale was only a scientific novelty. Fertile triticales capable of producing viable seed were virtually unknown until the late 1930's when a Swedish geneticist named Arne Muntzing produced fertile triticale by treating the hybrids with colchicines, which doubled the chromosome number allowing reproductive pairing and division to occur. With normal pairing and division, triticale could be reproduced through subsequent generations. Once a fertile hybrid of triticale was produced, it became possible to create new combinations between wheat and rye and to intercross triticale with various common wheat. Triticale became a new crop plant, similar to, but distinct from common wheat, rye, and other cereal grains in breeding, seed production, and use. Triticale is self-pollinating (similar to common wheat) and not cross-pollinating (like rye). Once created and reproduced, a triticale does not revert or break-down to its original wheat and rye components.
Breeding programs begun in the 1950's and 1960's in Poland, Mexico, Canada, and the U.S. pioneered the success of today's modern triticale varieties. Modern breeding programs concentrate on developing varieties with improved animal feed and fodder for production under diverse environmental conditions, as well as attempts to breed triticale varieties more suitable for human consumption. Triticale is managed like common wheat, though it requires fewer inputs such as water, fertilizer, and pesticides.
Most of the triticale grown in the United States is used for feed grain and forage for swine, dairy cattle, and poultry. Triticale competes with other cereal grains, primarily common wheat and oats, for these forage markets. These markets in the U.S. are substantial. Annually in the U.S., over 18 million acres of cereal grains are planted for forage production. In the southern Central Plains alone, over 12 million acres of common wheat are used for pasture for grazing on average each year. Cereal silage and hay are important in the major dairy producing regions, and cereal hay is a popular forage for horses.
Compared to common wheat and oats, triticale has important advantages for forage production in terms of yield, production costs, and tolerance to pests, drought, low fertility, mineral toxicities, and heavy grazing (National Research Council: A Promising Addition to the World's Cereal Grains, National Academy Press, Washington, D.C. 1989). Triticale is generally superior to all classes of common wheat for pasture, silage, hay, and for grain used for feed. Triticales, like common wheat, have either a winter or spring growth habit, but vary significantly in plant height, tend to tiller less, and have a larger inflorescence when compared with common wheat. The majority of triticale cultivars have prominent awns, which sometimes cause problems in pastures or in hay. Recent releases are awnless and have increased its potential use as forage.
Common wheat and triticale have many similarities in their pattern of plant development and morphology. The flower heads or spikes, develop at the top of the main stems and secondary stems called tillers, which are analogous to branches. An individual plant usually has a main stem and multiple tillers, the number of which depends on plant density, soil moisture, nutrient supply, pest damage, seeding date, and temperature, as well as the genetics of the plant. Typically, two to four tillers per plant will develop to the point of developing a head. Each head at the top of the stem consists of multiple spikelets, each of which consists of multiple florets that produce pollen, ovules, and ultimately, kernels.
World triticale production has increased nearly 50% from 1991 to 2001 (United Nations—FAOSTAT). According to the United Nations Food and Agriculture Organization, it is estimated that over 10 million acres and an average of 3,021 lb/acre were produced worldwide in 2004. Major producers include China, Poland, Germany, France, and Australia. Estimates in the United States alone approached 1 million acres in 2004.
Currently, most of the triticale that is grown in the United States is used for forage, and it is difficult to obtain statistical data on yield because it is not differentiated from wheat forage and other small grain forage in USDA reports. Most of the triticale acreage in the United States is in the Southern Plains as an annual cool-season pasture, while the remaining acreage is grown in either the Northern dairy states as forage, in the Southeast for silage, and in the Intermountain West for beef pasture.
Triticale has many benefits to offer crop producers, livestock feeders, and for commercial use in soft-dough mixtures. Its major strength is its versatility: it can be used for grazing, silage, feed, cover crops, straw, and even human consumption. Additionally, production of triticale provides environmental benefits such as erosion control and improved nutrient cycling through crop rotation. Thus, because of its considerable benefits, significant plant breeding effort has been directed towards breeding triticale.
There are numerous steps in the development of any novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single cultivar an improved combination of desirable traits from the parental germplasm. In triticale, the important traits include increased yield and quality, resistance to diseases and insects, resistance to drought and heat, and improved agronomic traits.
Choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of cultivar used commercially (e.g., F1 hybrid cultivar, pureline cultivar, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection.
The complexity of inheritance influences choice of the breeding method. Backcross breeding is used to transfer one or a few favorable genes for a highly heritable trait into a desirable cultivar. This approach has been used extensively for breeding disease-resistant cultivars. Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination, the frequency of successful hybrids from each pollination and the number of hybrid offspring from each successful cross.
Each breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria vary depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, overall value of the advanced breeding lines, and number of successful cultivars produced per unit of input (e.g., per year, per dollar expended, etc.).
Promising advanced breeding lines are thoroughly tested and compared to popular cultivars in environments representative of the commercial target area(s) for three or more years. The best lines having superiority over the popular cultivars are candidates to become new commercial cultivars. Those lines still deficient in a few traits are discarded or utilized as parents to produce new populations for further selection.
These processes, which lead to the final step of marketing and distribution, usually take from seven to twelve years from the time the first cross is made. Therefore, development of new cultivars is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.
A most difficult task is the identification of individuals that are genetically superior because, for most traits the true genotypic value is masked by other confounding plant traits or environmental factors. One method of identifying a superior plant is to observe its performance relative to other experimental lines and widely grown standard cultivars. For many traits a single observation is inconclusive, and replicated observations over time and space are required to provide a good estimate of a line's genetic worth.
The goal of a commercial triticale breeding program is to develop new, unique and superior triticale cultivars. The breeder initially selects and crosses two or more parental lines, followed by generation advancement and selection, thus producing many new genetic combinations. The breeder can theoretically generate billions of different genetic combinations via this procedure. The breeder has no direct control over which genetic combinations will arise in the limited population size which is grown. Therefore, two breeders will never develop the same line having the same traits.
Each year, the plant breeder selects the germplasm to advance to the next generation. This germplasm is grown under unique and different geographical, climatic and soil conditions, and further selections are then made, during and at the end of the growing season. The lines which are developed are unpredictable. This unpredictability is because the breeder's selection occurs in unique environments, with no control at the DNA level (using conventional breeding procedures), and with millions of different possible genetic combinations being generated. A breeder of ordinary skill in the art cannot predict the final resulting lines he develops, except possibly in a very gross and general fashion. The same breeder cannot produce, with any reasonable likelihood, the same cultivar twice by using the exact same original parents and the same selection techniques. This unpredictability results in the expenditure of large amounts of research moneys to develop superior new triticale cultivars.
Pureline cultivars of triticale are commonly bred by hybridization of two or more parents followed by selection. The complexity of inheritance, the breeding objectives and the available resources influence the breeding method. Pedigree breeding, recurrent selection breeding and backcross breeding are breeding methods commonly used in self pollinated crops such as triticale. These methods refer to the manner in which breeding pools or populations are made in order to combine desirable traits from two or more cultivars or various broad-based sources. The procedures commonly used for selection of desirable individuals or populations of individuals are called mass selection, plant-to-row selection and single seed descent or modified single seed descent. One, or a combination of these selection methods, can be used in the development of a cultivar from a breeding population.
Pedigree breeding is primarily used to combine favorable genes into a totally new cultivar that is different in many traits than either parent used in the original cross. It is commonly used for the improvement of self-pollinating crops. Two parents which possess favorable, complementary traits are crossed to produce an F1 (filial generation 1). An F2 population is produced by selfing F1 plants. Selection of desirable individual plants may begin as early as the F2 generation wherein maximum gene segregation occurs. Individual plant selection can occur for one or more generations. Successively, seed from each selected plant can be planted in individual, identified rows or hills, known as progeny rows or progeny hills, to evaluate the line and to increase the seed quantity, or, to further select individual plants. Once a progeny row or progeny hill is selected as having desirable traits it becomes what is known as a breeding line that is specifically identifiable from other breeding lines that were derived from the same original population. At an advanced generation (i.e., F5 or higher) seed of individual lines are evaluated in replicated testing. At an advanced stage the best lines or a mixture of phenotypically similar lines from the same original cross are tested for potential release as new cultivars.
The single seed descent procedure in the strict sense refers to planting a segregating population, harvesting one seed from every plant, and combining these seeds into a bulk which is planted the next generation. When the population has been advanced to the desired level of inbreeding, the plants from which lines are derived will each trace to different F2 individuals. Primary advantages of the seed descent procedures are to delay selection until a high level of homozygosity (e.g., lack of gene segregation) is achieved in individual plants, and to move through these early generations quickly, usually through using off-season nurseries.
Selection for desirable traits can occur at any segregating generation (F2 and above). Selection pressure is exerted on a population by growing the population in an environment where the desired trait is maximally expressed and the individuals or lines possessing the trait can be identified. For instance, selection can occur for disease resistance when the plants or lines are grown in natural or artificially-induced disease environments, and the breeder selects only those individuals having little or no disease and are thus assumed to be resistant.
In addition to phenotypic observations, the genotype of a plant can also be examined. There are many laboratory-based techniques available for the analysis, comparison and characterization of plant genotype; among these are Isozyme Electrophoresis, Restriction Fragment Length Polymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs), Arbitrarily Primed Polymerase Chain Reaction (AP-PCR), DNA Amplification Fingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs), Amplified Fragment Length polymorphisms (AFLPs), Simple Sequence Repeats (SSRs—which are also referred to as Microsatellites), and Single Nucleotide Polymorphisms (SNPs).
Isozyme Electrophoresis and RFLPs have been widely used to determine genetic composition. Shoemaker and Olsen, (Molecular Linkage Map of Soybean (Glycine max L. Merr.) p 6.131-6.138 in S. J. O'Brien (ed) Genetic Maps: Locus Maps of Complex Genomes, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., (1993)) developed a molecular genetic linkage map that consisted of 25 linkage groups with about 365 RFLP, 11 RAPD and three classical markers and four isozyme loci. See also, Shoemaker, R. C., RFLP Map of Soybean, p 299-309, in Phillips, R. L. and Vasil, I. K. (eds.) DNA-Based Markers in Plants, Kluwer Academic Press, Dordrecht, the Netherlands (1994).
SSR technology is currently the most efficient and practical marker technology; more marker loci can be routinely used and more alleles per marker locus can be found using SSRs in comparison to RFLPs. For example, Diwan and Cregan described a highly polymorphic microsatellite locus in soybean with as many as 26 alleles. (Diwan, N. and Cregan, P. B., Theor. Appl. Genet. 95:22-225, 1997.) SNPs may also be used to identify the unique genetic composition of the invention and progeny varieties retaining that unique genetic composition. Various molecular marker techniques may be used in combination to enhance overall resolution.
Molecular markers, which include markers identified through the use of techniques such as Starch Gel Electrophoresis, Isozyme Electrophoresis, RFLPs, RAPDs, AP-PCR, DAF, SCARs, AFLPs, SSRs, and SNPs, may be used in plant breeding. One use of molecular markers is Quantitative Trait Loci (QTL) mapping. QTL mapping is the use of markers which are known to be closely linked to alleles that have measurable effects on a quantitative trait. Selection in the breeding process is based upon the accumulation of markers linked to the positive effecting alleles and/or the elimination of the markers linked to the negative effecting alleles from the plant's genome.
Molecular markers can also be used during the breeding process for the selection of qualitative traits. For example, markers closely linked to alleles or markers containing sequences within the actual alleles of interest can be used to select plants that contain the alleles of interest during a backcrossing breeding program. For example, molecular markers are used in soybean breeding for selection of the trait of resistance to soybean cyst nematode, see U.S. Pat. No. 6,162,967. The markers can also be used to select toward the genome of the recurrent parent and against the markers of the donor parent. Using this procedure can attempt to minimize the amount of genome from the donor parent that remains in the selected plants. It can also be used to reduce the number of crosses back to the recurrent parent needed in a backcrossing program. The use of molecular markers in the selection process is often called Genetic Marker Enhanced Selection. Molecular markers may also be used to identify and exclude certain sources of germplasm as parental varieties or ancestors of a plant by providing a means of tracking genetic profiles through crosses as discussed more fully hereinafter.
Mutation breeding is another method of introducing new traits into triticale varieties. Mutations that occur spontaneously or are artificially induced can be useful sources of variability for a plant breeder. The goal of artificial mutagenesis is to increase the rate of mutation for a desired characteristic. Mutation rates can be increased by many different means including temperature, long-term seed storage, tissue culture conditions, radiation (such as X-rays, Gamma rays, neutrons, Beta radiation, or ultraviolet radiation), chemical mutagens (such as base analogues like 5-bromo-uracil), antibiotics, alkylating agents (such as sulfur mustards, nitrogen mustards, epoxides, ethyleneamines, sulfates, sulfonates, sulfones, or lactones), azide, hydroxylamine, nitrous acid or acridines. Once a desired trait is observed through mutagenesis the trait may then be incorporated into existing germplasm by traditional breeding techniques. Details of mutation breeding can be found in “Principles of Cultivar Development” by Fehr, Macmillan Publishing Company, 1993.
The production of double haploids can also be used for the development of homozygous varieties in a breeding program. Double haploids are produced by the doubling of a set of chromosomes from a heterozygous plant to produce a completely homozygous individual. For example, see Wan et al., Theor. AppI. Genet., 77:889-892, 1989.
Descriptions of other breeding methods that are commonly used for different traits and crops can be found in one of several reference books (e.g., Allard, 1960; Simmonds, 1979; Sneep, et al. 1979; Fehr, 1987).
Proper testing should detect any major faults and establish the level of superiority or improvement over current cultivars. In addition to showing superior performance, there must be a demand for a new cultivar that is compatible with industry standards or which creates a new market. The introduction of a new cultivar will incur additional costs to the seed producer, and the grower, processor and consumer; for special advertising and marketing and commercial production practices, and new product utilization. The testing preceding the release of a new cultivar should take into consideration research and development costs as well as technical superiority of the final cultivar. For seed-propagated cultivars, it must be feasible to produce seed easily and economically.
Triticale is an important and valuable field crop. Thus, a continuing goal of triticale plant breeders is to develop stable, high yielding triticale cultivars that are agronomically sound. The reasons for this goal are obviously to maximize yield and the quality of the final product for forage, silage, and human consumption. To accomplish this goal, the triticale breeder must select and develop plants that have the traits that result in superior cultivars.
The development of new triticale cultivars requires the evaluation and selection of parents and the crossing of these parents. The lack of predictable success of a given cross requires that a breeder, in any given year, make several crosses with the same or different breeding objectives.
The crossed or hybrid seed is produced by manual crosses between selected parents. Floral buds of the parent that is to be the female are emasculated prior to the opening of the flower by manual removal of the male anthers. At flowering, the pollen from flowers of the parent plants designated as male, are manually placed on the stigma of the previous emasculated flower. Seed developed from the cross is known as first generation (F1) hybrid seed. Planting of this seed produces F1 hybrid plants of which half their genetic component is from the female parent and half from the male parent. Segregation of genes begins at meiosis thus producing second generation (F2) seed. Assuming multiple genetic differences between the original parents, each F2 seed has a unique combination of genes.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification.